Means for defrosting cooling coils



Aug. 19, 1952 M. W. GARLAND MEANS FOR DEFROSTING COOLING COIL-S 1. IWILIL/f/ nil-m.muuulllllmmlh FIG. 2

Filed Sept. 3 1949 INVENTOR. M w. GARLAND ATTORNEY Patented Aug. 19, 1952 acomoz MEANS FOR nnrnosrmo coorimenon s- 1 l Milton W. Garland, waynesboro, Pa., assignorto"' .j '1' f.

- Frick 'Company,'-Waynesboro,.1Za.;.-a.:corpcration of Pennsylvania l ApplicationSentember 1, 1949,?Serial NoJ113ifi35? eclaims. (once-e103) air. is deposited on the. cooling unit. in the .form

of frost. iThis frost is .a relatively good heat insulating medium and if allowed to accumulate and remainon the coils materiallyim-pairs the efficiency of the coo'lingunit.

' To maintain the eificiency of the refrigeration system it is necessaryto. remove the accumulated frost in asshort a timeas possible in order to maintain a relatively low-temperature in the compartment and preclude the necessity of recooling the same from anelevated temperature after completion of the defrosting operation.

Numerous systems have been devised'for accomplishing the defrosting operation, among which are the provision of a heated body adjacent the cooling unit, the passage ofwarm air or gas over the cooling unit, and the shutting down of the refrigeration system inorder toallow the frost to melt. These attemptsto solve the defrosting problem have presenteddisadvantages, the most serious ofwhich is the relatively long defrosting cycle andthe excessive raising of thetemperature within therefrigerated compartment. Attempts have :also been made to solve the defrosting problem by-sprayi-ng arelatively warm fluid. such as water over: the cooling unit to. melt the frost accumulated thereon. This method has the advantage of melting the frost in a relatively short time without materially raising the temperature in the refrigerated compartment but there are also very serious disadvantages connected with this method as it has been heretofore employed.

For conveying the water to the coilsand distributing it thereover a spray head is ordinarily utilized, which is provided with a plurality of relatively small spray openings. At the completion of the defrosting ope-ration .allliquidmust be removed from the spray .head and'from the. pipe for conveying liquid thereto inorderto prevent its freezing and subsequently clogging for the next operation. Attempts 'have' beenmade to meet this problem by the provision 'of a selfdraining liquid supply conduit which is normally open to the atmosphere. In leaving the. conduit open to the atmosphere several undesirable consequences occur such as the likelihood of, passage of refrigerated air from or warm air to'the compartment, in addition to 'the likelihood of contaminationof the'refrigerated space bymeans of the open-connection. w

Furthermore; in an air unit in which fansare positioned over-the coils to-promote the circulation of air during normal cooling'operation the fan draws warm air-from the outside into. the refrigerated space through the normally open conduit. i

-Accordingly, it is an'objectof th'e presentinvention to provide a 'dr'afro'sting"system 'for :utilizing-a first relatively warm 'fluid such -as water.

for the defrosting operation -andfforutilizing a second fluid for positively'removing -all of=the first fluid remaining in the supply conduit and spray head-after the completion of the defrosting-"operation.

'A'furjther object of the invention is'to provide a'defrosting system utilizing-a relatively warm fluid such as waterto-remove 'the frost from a cooling unit-and in which means is provided for effectivelyxpreventing the escape of cold air from the interior of the refrigerated compartment and for preventing the influx: of warm air thereto after thedefrosting operation* is completed and for preventing i the 1 entrance I o-r contaminating substances.

It-is a furtherobject of the invention to provide an "automatic defrosting :system' utilizing relatively warmfiui-d such as water to remove the frostf-rom the cooling unitfthedefrosting cycle being initiated andautomatically controlled by electrical timing devices or by means responsive to the accumulation of frost on-the cooling unit.

Further objects and advantages "of the invention will becomeapparen't' from" the following descr'iptiontaken in conjunction-with the drawings certain parts in'sec'tion forgreater clarity;

Fig; 2, a schematicdiagram-of an electrical control-circuit for the defrosting system of Fig. 1.

With continued reference to the drawing, there I is shown in Fig. la refrigeration compartment H3 provided with conventionalinsulated walls" I l, a cooling unit orevaporator l2 of any desired form being disposed within the=compartment. The compartment 'Hl may be "of any-desired size and shape and cooling unit l2 of course is proportionately arranged in' accordance with the-requirements of theparticular compartment to'be refrigerated.

Immediately above thecoblingunit 12 is located a spray head I3 having a plurality of relatively small apertures I4 in the lower surface thereof, there being a suflicient number of these apertures arranged in a manner to supply a relatively warm fluid such as water over the entire surface of the cooling unit or coil I2. A fluid supply conduit I5 is connected by a joint It to the spray head I3, this conduit extendingthrough a wall of the compartment I 0,there being provided a suitable sealing means II in the wall of the compartment to prevent the leakage of air aroundthe conduit I 5.

The conduit I5 is connected by a conduit E5 to a tank I 8 of a second fluid such as compressed dry air, a valve I9 being positioned in the line I5 between the tank and the spray head l3. Between the valve and the spray head, a T fitting connects the pipes I5 and 15' to a conduit 2!- which is connected to a conduit 2 l by a T fitting 22. The T fitting 22 is connected to a conduit 23 of a water supply lineand has a valve 24 for regulating the supply ofwater. The conduit 2| has a check valve 25 for closing the pipe so'that the pipe I5 will not communicate with: the --at'- mosphere through the conduits '2] and 2I I The conduit 2| has an automatic drain valve 26 of the type which will permit a small amount of liquid to drain therethrough, as may occur in-the event of the valve not providing a perfectseal, but closes on the application of pressure from the water flowing through valve 24 under normal.

conditions'of operation.- The tank;l 8 may' have the supply of air replenishedv by suitable means such as a compressor or source of supply through a pipe 2! connected thereto.

In order to remove the defrosting liquid and the Water resulting from the melting frost from the compartment ID a drip pan 30 is locatedbeneath the cooling unit I2. The drip pan is'provided with a drain 3| extending exteriorly-ofthe compartment through a suitable sealing means 32 in one of the walls thereof. Connected to the outer end of the drain is a conventional U-shaped trap 34, the-opposite end ofwhich may discharge to the atmosphere or lee-connected to a sewer pipe 36. The trap 34 operating in a well known manner seals the drain 3| against the passage of gas under normal pressures in either direction and also prevents the entry of other contaminating substances into the compartment I0. Liquid supply conduit I5 and drain 3| may be formed of a relatively poor heat conducting material in order to restrict the flow of heattherethrough and maintain the efficiency. of the system. I

In the operation-of the system described above, and assuming anaccumulationof frost on the cooling coil I2 sufficient to require removal thereof, valve 24 in the water line is opened, the valve IS in the air line remaining closed, thus permitting the water to flow through conduit 2|, opening check valve 25, and conduit 85 to the spray head. Atthe same time the water enteringcom duit 2| closes the valve 26 to prevent the passage of Water therethrough. -Upon reaching the spray head I3 the liquidis discharged therefrom through the apertures I4 ina spray covering the outer surface of cooling unit I2. Due to the relatively high temperature of the liquid frost present on thesuriace of the cooling unit I2 is thereby melted. The defrosting liquid as well as the liquid resulting from the melted frost is col lected in the drip pan 3|] and drains therefrom through drain 3] and trap 34 to the, atmosphere or sewer pipe as the case may be.

Upon completion of the removal of frost from the cooling unit.l2 the, water valve 24 is closed,

be completely freed of water.

"Since the'air is compressed and dry it is obvious that the supply pipe head and sprays will After the water removing operation the valve I9 is closed; the storage tank I8 may be replenished with air as 1 required.

to M. B. Watts.

In-many installations it is desirable that the operation of the defrosting system be entirely automatic and accordingly there is illustrated in Fig. 2 an electrical control circuit which may be utilized in conjunction with the apparatus shown in Fig. 1 and described above for performing the defrosting operation at predetermined intervals. This may be accomplished by merely presetting a conventional timer for the desired cycle of operations within a predetermined period of time.

In the control system, the valves I9 and 24 are provided with operating solenoids 31 and 38 respectively, these solenoids being connected by suitable leads 39 and 40 to a conventional timer 4| for which power is supplied through lines 42. Where an electrically operated fan or blower is employed for circulating air over the coils during normal operation, the timer may control the operation of such fan by conventional switch means. Similarly, the refrigerant supply or return may be controlled .by the timer if desired.

The operation of the control system illustrated in Fig. 2 is initiated by the timer 4| to open and close the valves I9 and 24 at predetermined intervals. The invention also contemplates the use of the valve actuating timing means shown in Patent No. 2,480,346, issuedAugust 30, 1949 It will thus be seen that by the above described control circuit a relatively simple efficient means has been provided whereby the refrigerating equipment may be defrosted at predetermined intervals, the defrosting cycle being predetermined in accordance with the time required for such operation. v

' In certain refrigeration installations means is provided usually in the form of an electrically driven fan for circulating air within the refrigerated compartment and over the cooling unit to more efficiently cool the compartment and in installations such as these the motor for driving the circulating fan and the power supply there for may be conveniently utilized as a control means for a defrosting system such as thatshown in Fig. 1 and described above. 7 j

It is therefore apparent that bythis invention there has been provided a relatively, simple, inexpensive defrosting system which readily lends itself to manual operation and control, to, completely automatic control based on a predeterjmined cycle of operatio'n, and a predetermined period of time between cycles of operation and which may also be convenientlyjcontrolled by the degree of accumulation of frost on the cooling unit as shown in the Watts Patent 2,480,346. This defrosting system completely and rapidly removes the accumulated frost from the cooling unit while maintaining relatively low temperature in the refrigeration compartment. At the completion of the defrosting operation all of the liquid used to accomplish the defrosting is removed from the system thereby precluding the possibility of the systems being clogged by the subsequent formation of ice. Furthermore, the system is effectively closed after the defrosting operation in order to prevent the possibility of contamination of the compartment by the influx of gas or other substance as well as to prevent the passage of air into or from the compartment, lowering its efliciency.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

l. A refrigeration system comprising a refrigeration compartment, a cooling unit disposed in said compartment, a defrosting system for removing accumulated frost from said cooling unit, said defrosting system comprising a spray head disposed above said cooling unit, a drip pan disposed beneath said cooling unit, a drain connected to said drip pan and extending exteriorly of said compartment, a liquid trap in said drain, a supply conduit connected to said supply head and extending exteriorly of said compartment, said supply conduit being connected to a source of dry compressed air, an auxiliary conduit connected to said supply conduit and connected to a source of liquid, a first valve in said supply conduit between the source of air and the auxilary conduit connection, a second valve in said auxiliary conduit for controlling the supply of liquid and a check valve in said auxiliary conduit for preventing the flow of gases therethrough, a drain valve connected between the second valve and the check valve, said drain valve being adapted to permit a relatively small flow of liquid under low pressure through it but to prevent the passage of liquid through it under normal operating pressure, whereby upon closing of the first valve in the supply conduit and opening of the second valve in the auxiliary line the liquid may flow through the check valve into the spray head and be sprayed over the cooling unit thus melting the frost accumulated thereon, the liquid and melted frost being collected in the drip pan and removed from the compartment through the drain, and whereby upon closing the second valve in the auxiliary conduit and opening of the valve in the supply conduit, the check valve will close and dry compressed air may pass through the supply conduit and the spray head thus removing all of the liquid therefrom.

2. In a defrosting system for a refrigeration system having a compartment and a cooling unit with drainage means therefor, a defrosting system comprising conduit means for directing fluid to said cooling unit to melt accumulated frost, first and' second means for directing first and second fluids respectively to said conduit means, said first fluid being adapted to melt frost from said cooling unit, individual control means for I said first and second directing means, and valve in said first fluid supply means for controlling flow therethrough, a second valve connected into said first fluid supply means between said first valve and said first conduit, said second valve permitting fluid under low pressure reaching it to discharge from the first fluid supply means, a third valve in said first fluid supply means between said second valve and said first conduit, said third valve permitting flow therethrough toward the first conduit and preventing flow in a second fluid sup-ply the reverse direction, means connected to the first conduit, and valve means in the second fluid supply means.

4. The structure of claim 3, and electrical control means for operating the first valve in said first fluid supply means and the valve means in said second fluid supply means.

5. In a defrosting system having a compartment and a cooling unit therein, fluid directing means, a first fluid supply means connected to the fluid directing means for spraying a first fluid of relatively high temperature over said cooling unit to melt frost accumulated thereon, valve means in the first fluid supply means for controlling flow therethrough, auxiliary means in the first fluid supply means for positively preventing leakage through the valve means from reaching the fluid directing means, a second fluid supply means connected to the fluid directing means, and valve means in the second fluid supply means for controlling flow therethro-ugh.

6. The method of defrosting apparatus in a refrigeration compartment comprising supplying a first fluid of relatively high temperature to directing means positioned to distribute fluid over the apparatus to remove frost from the apparatus, the fluid passing from thedirecting means onto the apparatus, discontinuing I the flow of said first fluid when sufficient frost has been removed from the apparatus, and supplying a second fluid to the directing means to remove any first fluid remaining therefrom, saidsecond fluid passing through the directing means and into the compartment.

MILTON W. GARLAND.

REFERENCES CITED The following references are of record in the file of this patent: 

